I am very happy to announce the Live version of my open-source Stellar testnet wallet. Here is the code on Github.
This is for Stellar enthusiasts and anyone working on stellar smart contracts. Below, I’ll (1) explain why this tool is useful, (2) discuss some background information about Stellar smart contracts, (3) provide short answers to some of the most challenging questions I faced during development, (4) give brief instructions on how to use this tool, and (5) list some resources that I found helpful.
Disclaimer : I built this as an educational experiment and the program has not been thoroughly tested.
1. Why Build this Stellar Tool?
I work at a blockchain development company called web3devs. We’re probably most well known for our work on Ethereum smart contracts, but we also work with Stellar smart contracts!
Although Stellar.org explains the concepts behind Mutisignature Escrow Account with Time Lock & Recovery, and provides example codefor creating a multi-sig account, they do not show how to implement the time lock or recovery methods. With this post, I am releasing that code and a live demonstration of how it works.
2. Background Information
Most applications interact with the Stellar network through Horizon, a RESTful HTTP API server. See Stellar.org. You use a SDK to interact with Horizon. I used the Javascript SDK.
There are significant differences between Ethereum and Stellar smart contracts. For one thing, Ethereum smart contracts are written in Solidity, which is a Turing-complete language.
In contrast, stellar smart contracts can only accomplish a limited set of tasks. You use a common programming language like JavaScript or Go to You interact with Horizon, which is an interface between Stellar Core and applications that want to access the Stellar network.
3. Pernicious Bugs and Tricky Questions
Why Does My Transaction Keep Failing (Getting 400 Response from Horizon)?
- You didn’t set the base fee:
const baseFee = await server.fetchBaseFee();
const transaction = new StellarSdk.TransactionBuilder(account, {
fee: baseFee })
- You didn’t load the account before building the transaction:
const account = await server.loadAccount(sourceKeys.publicKey());
const transaction = new StellarSdk.TransactionBuilder(account, { fee: baseFee })
Why can’t I submit the Unlock XDR to Horizon?
You may be trying to submit the XDR too early. The unlock XDR can only be submitted after the lock-up period is over. This is a little confusing, because you have to create the unlock transaction before the lock-up period is over.
The solution is signing the unlock transaction, and saving that transaction somewhere publicly. Only submit the unlock xdr to Horizon once the lock up period is over.
try {
// Save as an XDR string
const transactionXDR = transaction
.toEnvelope()
.toXDR()
.toString("base64");
console.log("FN: unlock", "Success! Results:", transactionXDR);
return transactionXDR;
How do I set Timebounds?
It was not easy to figure out the syntax for setting timebounds. Here is what finally worked for me:
// The unlock date (D+T) is the first date that the unlock transaction can be
// submitted. If Transaction 3 (this transaction) is submitted before the
// unlock date, the transaction will not be valid.
const transaction = new StellarSdk.TransactionBuilder(escrowAccount, {
fee: baseFee,
timebounds: {
minTime: (
Math.floor(Date.now() / 1000) + parseInt(unlockTx.unlockDate)
).toString(),
// The maximum time is set to 0, to denote that the transaction does not have
// an expiration date.
maxTime: (0).toString()
},
sequence: (parseInt(escrowAccount.sequence) + 1).toString()
})
4. Instructions
In order to use this tool you’ll need to create at least two testnet accounts. You can make new accounts within the tool by clicking the “Create Stellar Account” button. Just take note of the public and private keys that pop up in the header. You can also use these pre-made test accounts:
Seller/Destination
Public Key: GCHVXWBLCPWRMAF7QNKPB22JJX6VYTMX2JQ5XAVMEM6PD5HRHF42EZIC SecretKey: SAI2UOI47OBALUI4YAUVPZ3QN3LTYM5CXP3MEKGQR64OWVSLT6M7Q2VK
Buyer
Public Key: GDEJU3BKAPMDP3SAXEE5C5T2IE6363ZSZMR7SS3YZTOQJZ3L24YJSZ4G Secret Key: SDCS7UCINHWVEWFUNHRXZRUU5WQ7ZAIPHXQNED4IBQ2U6Y45W72U22ST
Note: these are test accounts so no real money is involved. You should never post a secret key to an account on the public stellar server.
You can image one account as a “seller” (the Destination), and another as a “buyer”. The buyer creates the escrow account and adds the seller (Destination) as a signer. When the lockout period expires the seller can use the XDR to “unlock” funds in the escrow account.
5. Resources:
Here are some of the resources I found helpful:
- Stellar Laboratory:I constantly had this tab open to test various operations, transactions, etc.
- Michiel Mulders Article: Helps you get a little more familiar with the concept of account signers.
- Sylvain Faucherand Article: Covers a basic escrow account, but doesn’t address how to make it time-locked.
- Robert Durst Article: If you’re still scratching your head about account signatures.
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